In his 36 years as the men’s head basketball coach at Duke, Mike Krzyzewski has delivered countless motivational speeches to his players. On a cloudless, cool May Sunday morning, Coach K was again exhorting Duke students -- reminding them that attitude, belief, preparation and execution are the keys to being a part of a successful team -- except this time his words were directed at Duke’s Class of 2016 during the university’s 164th commencement ceremonies. “There’s nothing more important than attitude, and it’s your choice,” he said.